Interview: James McAvoy, Jon S Baird and Eddie Marsan talk Filth

The finest Irvine Welsh film adaptation since you-know-what, Filth memorably lives up to its title.
James Mottram scrubs himself down to chat with its director and stars

Talk about author support. When Irvine Welsh signed over the movie rights to his 1998 book Filth to director Jon S Baird, the Leith-born novelist vowed to get a tattoo in honour of their collaboration. ‘He said, “I’ll get the tattoo done if you get the film made,”’ recalls Baird, a former graduate of Aberdeen University. ‘I said, “do you think that’s wise? See if you like it first.”’

Baird did manage to get Filth on screen and Welsh – good to his word – got that tattoo: a pig wearing a policeman’s helmet taken from the book’s memorable cover illustration. ‘Irvine was really important to getting a buzz going about this film, and coming to meetings with financiers and distributors,’ adds Baird who directed the 2008 true-life football hooligan drama Cass. ‘He’s always been a champion of it.’

His enthusiasm is no surprise. Firstly, Filth features a scorching performance from James McAvoy as Bruce Robertson, one of Welsh’s foulest creations: a boozy, coked-up, womanising, scheming Detective Sergeant in the Lothian constabulary. As the story unfolds, Robertson begins to unravel. As McAvoy says: ‘You start to realise, “I’m just watching somebody who needs to be locked up, who is very sick. Fuck man: he needs help!”’

Secondly, Filth is the best Welsh adaptation since Trainspotting, Danny Boyle’s era-defining take on his groundbreaking novel about Leith heroin addicts. Other Welsh works put on film – The Acid House, Ecstasy – never quite nailed it. ‘There’s always the ghost of Trainspotting hanging over these things,’ says actor Eddie Marsan, who plays Clifford Blades, one of the characters tormented by Robertson.

Baird, however, truly captures the spirit of Filth’s creator, from the cartoon credits to the Clint Mansell score. Partly, this comes from ensuring every member of the cast and crew ‘empathised’ with what he was trying to do. ‘It was just about hiring the person who said, “I totally get Bruce”, and got the humour behind the darkness and the heightened sense of reality, which was very important.’

For 34-year-old Drumchapel-raised McAvoy, it meant a radical change from the nice-guy roles he’s been playing such as the patsy figure in Danny Boyle’s Trance. Early on, shooting around Glasgow, he noticed a gradual adjustment in his personality. ‘I’ve got quite a dirty and inappropriate sense of humour anyway, but I think it was worse while I was playing Bruce.’

By the final scenes, shot in Hamburg’s infamous red-light district, he’d let the character truly get under his skin. ‘I did get very fucked-up!’ he says. ‘I was eating bad and trying to feel like shit.’ So in-character was McAvoy, that he even goaded a real-life prostitute to punch him – she duly obliged. ‘Don’t get me wrong, I’m never going to be that guy who goes away with a mental problem after playing a part. It just felt like, “fucking hell, this film’s gonna kill me!”’

With support from a roster of great British actors – Shirley Henderson, Jamie Bell, Jim Broadbent and Imogen Poots among them – Filth may be dirty, but it’s unquestionably one of the most entertaining rides in British cinema this year. The only thing it isn’t, says Baird, is a critique of the boys in blue. ‘The last thing this film is about is police inspectors or detectives: they could be telesales workers or bin men. It’s all about the personality and the journey.’